This project deals with the problem of restoring lower limb function to patients who require the use of a knee-ankle-foot orthosis (KAFO) for ambulation and must have the knee locked for stability during gain. These patients typically have neuromuscular conditions which weaken or paralyze the knee extensors, the hip extensors, and the ankle plantar flexors. Currently, these types of patients are usually fitted with either a conventional KAFO which has a knee joint equipped with a mechanical manual lock, or a free-knee orthosis equipped with an eccentric knee joint. These orthotic schemes result in a lack of knee movement during the swing phase of gain, producing inefficient gait. The goal of this project is to design, develop, and test a small, lightweight, electronically controlled knee joint that can be installed on a conventional KAFO. The knee joint will unlock during the swing phase of gait and lock during the stance phase of gait. To accomplish this goal, plans are to: 1) perform design enhancements to the logic-controlled electromechanical free-knee orthosis which will yield a durable and reliable, totally integrated package; 2) perform objective measurements of gait patterns and metabolic energy requirements for the proposed orthosis, as compared to a locked KAFO; 3) test the reliability of the orthotic device on patients who require KAFOs for ambulation; and 4) document the outcome of patients who utilize the orthosis, based on clinical trials. The results of these studies are expected to improve the efficiency of gait in patients requiring conventional KAFOs. This orthosis will be useful for patients with poliomyelitis, spinal cord injuries, myopathic disorders, congenital spinal defects, and acquired paralysis due to infections or vascular insults.